The present invention relates to a card type memory device for use in an external memory device in a computer system for example, and method for manufacturing the same and, in particular, a card type memory device for holding a semiconductor chip with a nonvolatile semiconductor memory formed therein and method for manufacturing the same.
The external memory device for a computer system includes a detachable type relative to a device body to which it is connected, such as a floppy disk as a typical example.
In recent times, an IC memory card with a built-in semiconductor memory chip has been widely used. The floppy disk has the advantage of being very low in cost, freely detachable from an associated device body in a single operation and freely portable, but it has the limitation of being unstable in reliability and slow in access time and, if being made compact in size, involving less memory capacity in view of a narrowed area of its device body and achieving a compact device body to which it is connected.
On the other hand, the IC card has the advantage of being higher in reliability and faster in access time. However, since it has a two-piece connector insertable and withdrawable into and out of the associated device body, there is some inconvenience at a time of its being freely inserted and withdrawed into and out of the device body.
In the case where there is less amount of data to be handled, such as a characters, still images and speech data, and data has to be readily transferred between a plurality of devices, it is desirable to use such an external memory device having a reliability and high-speed characteristic. As a result, a greater demand has been made for such a device to be developed.
Under these situations, the applicant proposed a novel card type external memory device having a chip of a nonvolatile memory (for example, a flash EEPROM of NAND type), as a memory medium, built therein, capable of lowering an overhead cost, other than that of the memory chip, to a minimal extent, being readily insertable and withdrawable into and out of an associated device body and being easily portable (JPN PAT APPLN KOKAI PUBLICATION 7-37049) and called it as an SSFDC (Solid State Floppy Disk Card).
The card type external memory device is shown in a perspective view in FIG. 1 and has a structure as indicated in cross-section taken along line II--II in FIG. 1 as shown in FIG. 2.
As shown in FIGS. 1 and 2, a semiconductor package 110 is buried in a recess in a card type base board 120.
FIG. 3 is a perspective view showing the semiconductor package 110 withdrawn out of the base board, as shown in FIG. 2.
FIG. 4 is a cross-sectional view as taken along line II--II in an arrow-indicated direction in FIG. 3. The semiconductor package 110 has a memory chip 112 mounted on a through hole type double-sided printed board 111. The pad of the memory chip 112 is electrically connected by a corresponding wire 114 to a print pattern 113 on a chip mount surface of a double-sided printed board.
And the surface side (chip mount side) of the printed board 111 is sealed by a resin 115 to cover the memory chip 112 and wire bonding 114. The print pattern 116 on the rear surface side of the printed board 111 is used as a flat-surface terminal electrode for external connection.
FIG. 5 shows the rear surface of the printed board 111.
The card type base board 120 has the package storable recess in one surface of the card type insulating resin such that, in the recess, the electrode surface of the semiconductor package 110 is exposed substantially flush with the external surface of the base board.
If, in this case, use is made of, as a memory chip 112, a chip of a nonvolatile memory of a 16M bit memory capacity, such as a NAND type flash EEPROM chip, it is possible to realize a 2 M-byte memory capacity and achieve a unit exceeding 1.4 M bytes, a typical memory capacity of a floppy-disk.
In the present time, the memory chip mount printed board 111 as shown in FIG. 4 almost always uses a resin board but further improvement of the quality-retaining characteristic is demanded.
There is a growing demand that the structure of a semiconductor package built in the conventional card type external memory device as well as its manufacturing process be further simplified.